It is now well established that variations is early experience can produce changes in neuronal organization. The functional significance of these neurological alterations and the mechanisms by which they, occur, however, remain unknown. The present proposal is directed toward study of early environmental influences on the development of brain morphology and behavior, using the monocularly deprived rat as a model system. It is concerned most directly with perceptual capacities, specifically with: (1) how visual perception is modified by limiting postnatal experience, and (2) how such environmental influences on behavior are mediated by changes in cortical morphology, with particular emphasis on dendritic spines. In addition, the relationship between early sensory stimulation and local cerebral blood flow will also be examined and correlated with morphological and behavioral development. Finally, attempts will be made to mitigate the morphological and behavioral deficits produced by early sensory deprivation.